Many offices are equipped with scanners or multiple function peripherals (MFP) nowadays. The scanning equipment scans drawings, articles, and photos and saves them as image files. For the sakes of cost and visual effect, plastic is generally introduced as a material for the base plate of the scanning equipment.
Some do not consider plastic the best choice as a material for the base plate. First of all, plastic tends to deform when the temperature substantially changes. It is almost impossible to avoid the change of temperature when shipping or operating the scanning equipment, and therefore an environmental test is required for the scanning equipment to ensure its quality. The environmental test is generally carried out under a range of temperature from −40° C. to +70° C. Exposing to such severe environmental conditions, the plastic base plate suffers from large deformation and cannot remain level. Second, plastic is not durable. Collision is usually unavoidable when shipping and operating the scanning equipment, and it results in the deformation of the base plate. The precise function of the scanning equipment cannot be brought into full play as designed when such an unacceptable deformation occurs.
FIG. 1 illustrates the driving device for the scanner of the prior art. An active gear wheel 11 and a passive gear wheel 12 are directly connected to a plastic base plate 14 of the scanner, and a driving belt 13 is engaged with the active gear wheel 11 and the passive gear wheel 12. A scanning module (not shown) is connected to and driven by the driving belt 13 by means of a connecting component (not shown). When the driving belt 13 is driven by the active gear wheel 11, the scanning module is pulled forward by the driving belt 13 accordingly. A rigid component is disposed on the plastic base plate 14 as a guiding track 15 for the scanning module so that the scanning module moves forward along the guiding track 15 and proceeds in the same direction.
Because the active gear wheel 11 and the passive gear wheel 12 are respectively directly connected to the plastic base plate 14, there is relative displacement between the active gear wheel 11 and the passive gear wheel 12 when the plastic base plate 14 deforms. The relative displacement between the active gear wheel 11 and the passive gear wheel 12 affects the tension of the driving belt 13. One of the solutions is to introduce a metal base plate to avoid deformation of the base plate 14. However, introducing metal materials for the base plate 14 results in increase of production cost and worse portability and appearance.